1. Field of the Invention
The present invention relates to a method and a system for conducting a depth restoration process with respect to a depth map.
2. Description of the Related Art
At present, a human machine interaction system is being widely used in various fields. In particular, a hand gesture control system is very popular. An effective hand gesture control system may provide a kind of convenient operation method in the human machine interaction system.
As well known, regarding a hand gesture recognition system on the basis of an image and/or vision, its recognition accuracy is easily influenced by the quality of an input image especially when recognizing some special hand gestures such as those related to a sign language and fingertips. As a result, how to obtain a high quality image, by which it is easy to recognize a specific object thereof, becomes a very important problem. In a conventional human machine interaction system, in order to locate and segment a specific object, for example, a hand of a human body in an input image to be recognized, it is necessary to let a user wear, for example, a special glove having a predetermined color. By utilizing this kind of system, it is possible to easily and effectively locate each finger of the human hand. However, this kind of system is very sensitive to its environment. That is to say, when this kind of system is utilized, for example, the color of the special glove must be different from the background color. As a result, the application range of this kind of system is restricted. At the same time, since the user must wear, for example, the special glove in the process of utilizing this kind of system, this may result in not only inconvenience but also high cost.
With the development of an image processing technique, a color image has been used to conduct recognition and segmentation with respect to a human hand in the color image recently. Although this kind of method is simple and effective, it is also easily affected by a similar background color or a lighting condition.
Furthermore, with the improvement of the performance of a 3D camera, the 3D camera has been also involved in the human machine interaction system recently. By using a depth map captured by the 3D camera, it is possible to conveniently segment a part of a human body on the basis of a depth threshold value.
For example, in U.S. Pat. No. 6,911,995 B2, a kind of segmentation method is proposed in which first, by using a stereo camera, a current image and a background image of a scene are captured; then, by subtracting the background image from the current image, a foreground image is acquired; and then, on the basis of a predetermined depth threshold value, a segmentation process is conducted with respect to an area including fingertips. However, in this patent, only the predetermined depth threshold value is used to conduct the segmentation with respect to the fingertip area. As a result, in a process of conducting pixel point matching with respect to a multi-angle image so as to obtain a depth map, the boundary of the depth map is easily influenced by noise. This may result in loss of depth values of some pixel points or giving incorrect depth values to some pixel points.
Moreover, in a paper entitled “Depth Seeds: Recovering Incomplete Depth Data Using Superpixels” (WACV 2013: Workshop on Application of Computer Vision) and written by Michael Van den Bergh, an expansion method on the basis of a seed pixel point is proposed for recovering the lost depth information of some pixel points so as to obtain a more real depth map. In particular, this method includes pixel block level update and pixel level update. In a pixel block level (layer), color histogram based statistical information is adopted, and in a pixel level (layer), both color information and depth information are adopted. However, although this method is effective for processing a large object, it does not have a beneficial effect on recovering detailed information.